term:

Avulsion

avulsion n

[Latin avulsio act of tearing away, from avellere to tear away, from a- off, away + vellere to pull, pluck]
: a sudden cutting off of land by flood or change in the course of a body of water
;esp
: one that separates a portion from one person's property and joins it to the property of another compare accretion

Source: Merriam-Webster's Dictionary of Law ©1996. Merriam-Webster, Incorporated. Published under license with Merriam-Webster, Incorporated.